<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

<input type="button" value="0" id="btn1">
<script>
    var btn1 = document.getElementById('btn1');
    btn1.onmousedown = function(e){//event e evn event
        console.log(e);
    }
    btn1.onmouseup = function(e){//event e evn event
        console.log(e);
    }

    btn1.onmouseover = function(e){//event e evn event
        console.log(e);
    }
    btn1.onmouseout = function(e){//event e evn event
        console.log(e);
    }


</script>
</body>
</html>